Help... =(

I got a version 3.1 modchip and a version V4 ps2 (no gap), I got my cousin who's like 25 to solder everything, but now it won't boot... we reassemble it, it makes a quick flash at start, then nothing happends... does anyone have anything that can recomment me doing? =/

PS- his brother couldn't wait a couple days and he opend up the dvd-drive and took out my Capcom vs SNK 2 cd (the drive was completely out and stuff), im wondering, could that have anything to do with it?